The invention relates generally to the field of ultrasonic imaging, and in particular to the imaging of body lumens or cavities. More specifically, the invention relates to the use of imaging devices that are rotated at high speeds to produce an image of a body lumen or cavity.
The use of rotatable imaging devices to produce an image of a body lumen is well known. For example, one pioneering effort is described in U.S. Pat. No. 4,794,931, the complete disclosure of which is herein incorporated by reference. In U.S. Pat. No. 4,794,931, a drive cable having an imaging element at a distal end is rotated within a catheter to product an image of a diseased region prior to therapy.
Recently, there has been an advancement in the field of rotatable imaging devices where the size of the imaging devices has been substantially reduced. For instance, one such imaging device is described generally in copending U.S. application Ser. No. 09/017,578, filed Feb. 3, 1998, the complete disclosure of which is herein incorporated by reference. Such an imaging device is small enough to operate within traditional guide wire lumens of therapeutic catheters, such as angioplasty balloon catheters.
One potential problem that may arise when operating imaging devices within catheter lumens having a distal exit port, such as within guide wire lumens of therapeutic catheters, is that the rotating imaging device may accidentally be advanced beyond the distal exit port and into the body lumen, thereby posing a risk of damage to the luminal wall.
Hence, it would be desirable to provide a way to prevent the unwanted advancement of a rotating imaging device beyond a distal exit port of a catheter. Such a safeguard should be reliable and easy to use to maximize its acceptance in the industry.
The invention provides exemplary techniques for preventing the unwanted advancement of a rotating imaging device beyond an exit port of a catheter and into a body lumen. In one exemplary embodiment, a catheter is provided which comprises a catheter body having a proximal end, a distal end and a lumen, such as a guide wire lumen, which terminates in an exit port at the distal end. An ultrasonically recognizable pattern is disposed proximally to or at the exit port. The recognizable pattern is provided to produce a unique image when imaged with an imaging element of an imaging device which is rotated within the lumen.
The catheter is preferably included as part of a system which includes a controller having a motor to rotate the imaging device. The controller is configured to stop rotation of the imaging device upon receipt of a signal from the imaging device indicating that the presence of the recognizable pattern has been detected. In this way, once the imaging device has been advanced through the lumen and up to the recognizable pattern, the presence of the pattern will be detected by the controller which will stop rotation of the imaging device. As such, if the imaging device is advanced beyond the exit port, the imaging device will not be rotating, thus substantially reducing the chances of damaging the luminal or cavity wall. Alternatively, if the motor is employed to also translate the imaging device, the signal may be employed to stop translation of the imaging device so that the rotating imaging device will not be advanced distally beyond the exit port.
A wide variety of recognizable patterns may be provided to indicate when the imaging device has advanced too far within the lumen. For example, the pattern may comprise a tubular reflective member which is crimped or otherwise attached about the tubular body. Other patterns which may be employed include ultrasonically reflective materials having a variety of shapes and sizes which may be attached to or integrally formed within the catheter body, echogenic coatings, changes in the diameter of the catheter body, the distal end of the catheter body, and the like. Preferably, the pattern is fashioned to have a shape or configuration which allows it to be differentiated from the rest of the image. For example, the pattern may include a plurality of elongate apertures which will appear as voids in the resulting image, thus differentiating the pattern from a stent. As the controller recognizes the voids, rotation of the imaging device is stopped.
The catheter is preferably a therapeutic catheter having a therapeutic element for treating a region of the body lumen. For example, the therapeutic element may comprise an angioplasty balloon. As another example, the therapeutic element may comprise a stent delivery system. As a further examples, the therapeutic element may comprise a laser or a rotatable cutting element.
In another aspect, the lumen preferably extends the length of the catheter body. In this way, the catheter may be inserted into the body lumen over a guide wire in an over-the-wire manner. Typically, the lumen will have a diameter in the range from about 0.25 mm to about 5 mm, and from about 0.25 mm to about 0.5 mm for applications within the coronary arteries. The imaging device preferably has a diameter in the range from about 0.20 mm to about 2 mm.
The invention further provides an exemplary attachment for a catheter that has a lumen terminating in an exit port at a distal end of the catheter. The attachment comprises a tubular member which may be coupled about the catheter proximal to the exit port. The tubular member is constructed of an ultrasonically reflective material and has a unique shape that will produce a unique image when imaged with an ultrasonic imaging element which is rotated within the lumen. In this way, a catheter may be conveniently modified so that it may be used with a safety system that will stop rotation of an imaging element upon detection of the tubular member.
In one exemplary method of the invention, a body lumen is visualized by introducing a catheter into the body lumen. The catheter comprises a catheter body having a lumen which terminates in an exit port and an ultrasonically recognizable pattern disposed at or near the exit port. An imaging device is introduced through the lumen and positioned so that an imaging element is at a location that is to be imaged. The imaging device is rotated while the imaging element is actuated to produce an image of the body lumen. Rotation of the imaging device is stopped if an image of the pattern is detected so that advancement of the rotating imaging device beyond the exit port is prevented. Alternatively, translation of the imaging device may be stopped so that the rotating imaging device will not moved distally beyond the exit port.
In one aspect, the catheter is introduced into the body lumen by advancing the catheter over a guide wire. Once properly positioned, the guide wire is withdrawn and the imaging device is introduced into the guide wire lumen.
In another aspect, a therapeutic element is deployed while the imaging device is rotating to produce an image of the therapeutic element. In this way, the body lumen may be visualized throughout the therapeutic procedure. For example, visualization may occur while a balloon is being inflated or a stent is being deployed. The pattern preferably has a unique shape to allow it to be easily differentiated from the therapeutic element. In this way, once the unique shape is detected, rotation of the imaging device may be stopped.